Question

A carnot engine, whose efficiency is 40% takes in heat from a source maintained at a temperature of $500\text{K}$. It is desired to have an engine of efficiency 60%. Then, the intake temperature for the same exhaust (sink) must be

• A. efficiency of carnot engine cannot be made larger than 50%
• B. $1200\text{K}$
• C. $750\text{K}$
• D. $600\text{K}$

Answer 1

The correct option is C $750\text{K}$

Let the sink temperature be $T_s$, then
$1-\frac{T_s}{500}=0.4\therefore T_s=300\text{K}$
For second case, $1-\frac{300}{T}=0.6$
$T=\frac{300}{0.4}=750\text{K}$